Smartphone applications (apps) software environment limits the communications between an app and a SIM-card applet. Most smartphone operating systems do not offer any API (application programming interface) for SIM-card applet access. Some smartphones offer app developers access to the mobile equipment's identity, while others only offer access to the unit identity with no relationship to the identity parameters stored in SIM card.
SIP (Session Initiation Protocol) is a signaling communications protocol generally used for controlling communication sessions, including voice and video, over Internet Protocol (IP) networks. Mobile operators offering SIP clients for their mobile subscribers based on passwords for SIP registration might experience that SIP registration is initiated from another device than the mobile equipment containing a SIM card associated with the mobile subscription MSISDN. MSISDN (mobile subscriber) is an identification uniquely identifying a mobile subscription.
Mobile operators offering SIP on Wi-Fi integrated on the mobile subscription MSISDN will experience that HLR (Home Location Register) is not updated with the presence information from a mobile equipment registered on a SIP server. Incoming calls received when the SIP client is outside Wi-Fi network coverage will not reach the end-user SIP client mobile equipment while the calling party will experience a no-answer call attempt from the mobile operator.
Several pieces of mobile equipment (mobile devices) can be associated with a mobile subscription. Each device will contain a SIM card and the mobile identity will be used to identify the mobile station. A subscriber with a Twin SIM subscription can use two devices for mobile services. Routing preferences in the mobile operator will direct incoming calls to the preferred device in the case that both devices is available for receiving calls. In a case where the Twin SIM concept is applied to a combination of a SIP client and a standard GSM user on the same mobile equipment, incoming calls directed towards the SIP client while the mobile equipment is outside the Wi-Fi coverage will not be answered. This may result in a long delay before the call is redirected to the Twin over GSM.
U.S. 2007/254648 relates to a system for using dual mode handsets or «softphone» clients for voice, message and data services. The system includes, i.a., a SIP user agent with SIM based authentication and location update. U.S. 2007/254648 ensures that SIM and SIP user agent are co-located in the same ME by using internal communication on the device. However, no open APIs exist for a smartphone App to communicate with the SIM card. So the SIP user agent in U.S. 2007/254648 cannot be implemented as an Sip Client App.
There is need for an improved, secure method for determining that a SIM and a SIP client are co-located in the same ME, in particular without relying on direct, internal communication between the SIM and the SIP client.